Thermographic methods and products



@25 79 M5? .f-x. NWM/m 3,3@2565 THERMOGRAPHC METHODS AND PRODUCTS Filed Sept. 19, 1953 INVENTOR, @55 Af@ @vr/mf? United States Patent O 3,302,565 THERMOGRAPHC METHGDS AND PRODUCTS Douglas A. Newman, Glen Cove, N.Y., assigner to Columbia Ribbon and Carbon Manufacturing Co., Inc., Glen Cove, N.Y., a corporation of New York Filed Sept. 19, 1963, Ser. No. 309,924 9 Claims. (Cl. lill-149.2)

This invention relates to a new and improved method for applying images to a copy or master sheet such as a planographic printing plate by means of an imaged original sheet and infrared radiation, and to the novel master sheets for use in such process.

The planographic printing process is possibly the most popular process in use today for the reproduction of numerous copies of original subject matter. According to Isuch process, the original subject matter is inscribed in the form of images of oleophilic composition on the hydrophilic surface of a planographic printing plate. The plate is then mounted on a printing machine and moistened with oleophilic printing ink which is attracted by the oleophillic images on the hydrophilic printing surface of the plate and repelled by the Aremainder of the hydrophilic plate surface. The oleophilic ink, in the form of the images, is then transferred indirectly to a series of copy lsheets so that one thousand or more duplicate copies of the original subject -matter may be formed from the single plate.

It has been proposed that the oleophilic images may be applied `directly to a planographic printing plate by means of an imaged original sheet, an oleophilic transfer Sheet and infrared radiation, Such a process, as taught for instance by U.S. Patent No. 2,808,777, has met with some success but also involves certain limitations which require that the planographic plate be very translucent or that the sheet bearing the original images be very translucent and have images on only one side thereof. This is so because of the fact that the superposition of the original sheet, transfer sheet and plate requires that the infrared radiation must be nnimpeded from being absorbed by the original images Which it is desired to duplicate, and the radiation must not 'be absorbed by any other materials which lie between the original sheet and the plate.

If it is desired to copy an opaque original sheet or one having images on both sides thereof, such as a page from a book, it is necessary that such page be placed at the bottom of the superposed sheets with the images to be duplicated facing up, and to use a translucent planographic plate which will allow the infrared radiation to pass therethrough and be absorbed by the original images. Such translucent plates, based upon parchment paper or plastic film, have been difficult to develop with commercial success in that they present physical problems such as tackiness and curling, do not have suicient hydrophilic or Water resistance properties, and cannot be used as long run plates in that they do not provide more than a few hundred duplicate copies.

A conventional planographic printing plate may be imaged in the known thermographic process but only in such cases where the original sheet i-s translucent and carries images on only one side thereof. This is so because conventional plates are ibased upon relatively opaque heavy paper stock having good wet strength properties and do not transmit infrared radiation to any real extent. Most of the radiation appears to be reflected or dissipated by the plate surface and only small amounts of the radiation are absorbed by the plate and/or transmitted thereby depending upon the relative thickness and opacity of the particular plate used. Therefore the use of a conventional plate in the thermographic process Mice is limited to its use on the bottom of the pile of superposed sheets furthest from the radiation source, so that the original `sheet must be of a limited nature as indicated.

With these problems in mind, it is an object of the present invention to provide a thermographic process for imaging planographic printing plates, using any type of imaged original sheet and using any type of copy sheet.

It is another object of the invention to provide a thermographic process for imaging opaque planographic printing plates using relatively opaque original sheets o1' original sheets having images on both sides thereof.

These and other Objects and advantages of the present invention will be clear to those skilled in the art in the light of the present disclosure, including the accompanying drawing in which:

FIGURE l is a diagrammatic cross-section, to an enlarged scale, of a donor sheet, a transfer sheet and an imaged original sheet superposed under the effects of infrared radiation according to the first step of the present method.

FIG. 2 -is a diagrammatic cross-section, to an enlarged scale, of the donor sheet imaged according to FIG. 1

superposed with a planographic printing plate under the effects of infrared radiation.

FIG. 3 is a diagrammatic cross-section, to an enlarged scale, of the planographic printing plate imaged according to FIG. 2.

The present objects and advantages are accomplished according to this invention which provides a novel twostep thermographic process which allows for the formation of images on an opaque planographic printing plate, corresponding to images on any type of original sheet, such as an opaque or two-sided original sheet, by thermographic means.

The present process is composed of two separate and distinct steps, the first step comprising the formation of images on a donor sheet directly from an imaged original sheet, a transfer sheet and infrared radiation, and the second step comprising the heat transfer of said images from said donor sheet to the planographic printing plate.

According to the first step of the present method, as illustrated by FIG. 1 of the drawing, an imaged original sheet 30 which is opaque and/ or has front infrared radiation-absorbing images 31 and back infrared radiationabsorbing images 32 thereon is superposed with a transfer sheet 20 and a donor sheet 10 so that the original sheet is at the bottom of the pile furthermost from the radiation source S0.

The transfer sheet 20 and transfer layer 21 thereon must be free of materials which absorb infrared radiation to any substantial degree so as to permit the radiation to pass through to the original. The transfer sheet must be based upon a translucent foundation such as tissue paper or a clear plastic film such as Mylar or the like.

The transfer layer used according to the present invention is one based upon heat-tackiiiable, heat-meltable wax composition including, if desired, small amounts of resinous additives such `as VistaneX or lndopol which are isobutylene resins. The preferred Wax binders include the relatively soft waxes such as parafiin WaX and beeswax. The transfer layer consists of oleophilic Wax composition substantially free of pigments or dyes except for the presence of a tint color for proofreading purposes.

The donor sheet 10 must also be translucent and free of materials which absorb infrared radiation to any substantial degree. The donor sheet surface must have good receptivity for the heat-transferable composition of layer 21 and yet must freely release said composition to the v copy sheet or plate when heated in the second stepV of of imaging composition to soften and adhere to the treated surface of the donor sheet;

(c) separating t-he transfer sheet and donor sheet whereby .portions of the imaging composition remain adhered to the donor sheet in the form of oleophilic images corresponding to the original images;

(d) superposing the imaged donor sheet with a planographic printing plate having a nonmelting infrared radiation-absorbing layer thereon so that the images on the donor sheet are in surface contact with the printing surface of the plate, and applying infrared radiation to said plate to heat the plate and cause said images to soften and adhere to the plate surface; and

(e) separating the donor sheet and the planographic printing plate whereby the images remain adhered to the plate surface and transfer from the surface of the donor sheet in the form of oleophilic images corresponding to the original images.

3. The method according to claim 2 in which the treated surface of the paper donor sheet comprises a resinous coating.

4. The method according to claim 2 in which the treated surface of the paper donor sheet is calendered.

5. The method according to claim 2 in which the treated surface of the paper donor sheet is glazed.

6. The method Iaccording to claim 2 in which the planographic printing plate is one which has a layer of infrared radiation-absorbing material on the surface opposite to the printing surface.

7. The method of forming on a planographic printing plate oleophilic images which correspond exactly to images on an original sheet, which comprises the steps of:

(a) superposing an original sheet having thereon infrared radiation-absorbing original images, a transfer sheet comprising a translucent foundation carrying a layer of heat-transferable oleophilic imaging composition which does not absorb infrared radiation, and a thin translucent plastic film donor sheet Ihaving a treated su-rface yhaving Igood receptivity for said heat-transferable imaging composition and having the ability to release said imaging composition to the surface of a planographic plate under the effects of heat, the treated surface of said donor sheet being in surface contact with said imaging composition;

y(b) applying infrared radiation to said original images through said donor and transfer sheets for a period of time suflicien-t to selectively heat said original ima-ges and cause corresponding areas of the layer of imaging composition to soften and adhere to the treated surface of the donor sheet;

(c) separating the transfer sheet and donor sheet whereby portions of the imaging composition remain adhered to the donor sheet in the form of oleophilic images corresponding to the original images;

(d) superposing the imaged donor sheet with a planog-raphic printing plate having a non-melting infrared radiation-absorbing layer thereon so that the images on the donor sheet are in surface contact with the printing surface of the plate, and applying infrared radiation to said plate to heat the plate and cause said images to soften and adhere to the plate surface; and

(e) separating the donor sheet and the planographic printing plate whereby the images remain adhered to the plate surface and transfer from the surface of the donor sheet in the form of oleophilic images corresponding to the original images.

8. The method according to claim 7 in which the treated surface of the plastic film comprises a resinous coating.

9. The method according to claim 7 in which the treated surface of the plastic film is etched.

References Cited by the Examiner UNITED STATES PATENTS 3,007,829 11/1961 Akkeron 117--3.2 X 3,089,953 5/1963 Lind et al. 3,122,998 3/1964 Raczynski et al. 101--149-2 3,148,617 9/1964 Roshkind lOl-149.5 X 3,151,549 10/1964 Oransky et al. 10'1-149.2

ROBERT E. PULFREY, Primary Examinez'.

WILLIAM B. PENN, Examiner.

I. A. BELL, Assistant Examiner. 

2. THE METHOD OF FORMING ON A PLANOGRAPHIC PRINTING PLATE OLEOPHILIC IMAGES WHICH CORRESPOND EXACTLY TO IMAGES ON AN ORIGINAL SHEET, WHICH COMPRISES THE STEPS OF: (A) SUPERPOSING AN ORIGINAL SHEET HAVING THEREON INFRARED RADIATION-ABSORBING ORIGINAL IMAGES, A TRANSFER SHEET COMPRISING A TRANSLUCENT FOUNDATION CARRYING A LAYER OF HEAT-TRANSFERABLE OLEOPHILIC IMAGING COMPOSITION WHICH DOES NOT ABSORB INFRARED RADIATION, AND A THIN TRANSLUCENT PAPER DONOR SHEET HAVING A SMOOTH TREATED SURFACE HAVING GOOD RECEPTIVITY FOR SAID HEAT-TRANSFERABLE IMAGING COMPOSITION AND HAVING THE ABILITY TO RELEASE SAID IMAGING COMPOSITION TO THE SURFACE OF A PLANOGRAPHIC PLATE UNDER THE EFFECTS OF HEAT, THE TREATED SURFACE OF SAID DONOR SHEET BEING IN SURFACE CONTACT WITH SAID IMAGING COMPOSITION; (B) APPLYING INFRARED RADIATION TO SAID ORIGINAL IMAGES THROUGH SAID DONOR AND TRANSFER SHEETS FOR A PERIOD OF TIME SUFFICIENT TO SELECTIVELY HEAT SAID ORIGINAL IMAGES AND CAUSE CORRESPONDING AREAS OF THE LAYER OF IMAGING COMPOSITION TO SOFTEN AND ADHERE TO THE TREATED SURFACE OF THE DONOR SHEET; 